6.15.1
XV. ὃ δ’ ὡς ἑαυτὸν ἑώρα μὴ ἐπαρκοῦντα τῇ τῶν θείων βαθυτέρᾳ σχολῇ τῇ τε ἐξετάσει καὶ ἑρμηνείᾳ τῶν ἱερῶν γραμμάτων καὶ προσέτι τῆ τῶν προσιόντων κατηχήσει μηδ’ ἀναπνεῦσαι συγχωρούντων αὐτῷ, ἐφ᾿ ἑτέροις ἐξ ἕω καὶ μέχρις ἑσπέρας ἐπὶ παρ’ αὐτῷ διδασκαλεῖον φοιτώντων, διανείμας τὰ πλήθη, τὸν Ἡρακλᾶν τῶν γνωρίμων προκρίνας, ἔν τε τοῖς θείοις σπουδαῖον καὶ ἄλλως ὄντα λογιώτατον ἄνδρα καὶ φιλοσοφίας οὐκ ἄμοιρον, κοινωνὸν καθίστη τῆς κατηχήσεως, τῷ μὲν τὴν πρώτην τῶν ἄρτι στοιχειουμένων εἰσαγωγὴν ἐπιτρέψας, αὐτῷ δὲ τὴν τῶν ἐν ἕξει φυλάξας ἀκρόασιν.
XV. But when he saw that he was becoming unable for the deeper study of divine things, namely, the examination and translation of the sacred writings, and in addition for the instruction of those who were coming to him and did not give him time to breathe (for one batch of pupils after another kept frequenting from morn to night his lecture-room), he made a division of the numbers. Selecting Heraclas from among his pupils, a man who was zealous for divine things and, as well, a very learned person and no tyro in philosophy, he gave him a share in the task of instruction, assigning to him the preliminary studies of those who were just learning their elements, and reserving for himself the teaching of the experienced pupils.